1. Field of the Invention
This invention pertains to an implant for passing blood flow directly between a chamber of the heart and a coronary vessel. More particularly, this invention pertains to such an implant with an enhance design for promoting a healed layer of cells on an interior of the implant.
2. Description of the Prior Art
Commonly assigned U.S. Pat. No. 5,755,682 issued May 26, 1998 and commonly assigned and co-pending U.S. patent application Ser. No. 08/882,397 filed Jun. 25, 1997, entitled xe2x80x9cMethod and Apparatus for Performing Coronary Bypass Surgeryxe2x80x9d, and filed in the name of inventors Mark B. Knudson and William L. Giese (published as PCT International Application Publication No. WO 98/06356) both teach an implant for defining a blood flow conduit directly from a chamber of the heart to a lumen of a coronary vessel. In one embodiment, an L-shaped implant is received within a lumen of a coronary artery and passed through the myocardium to extend into the left ventricle of the heart. The conduit is rigid and remains open for blood flow to pass through the conduit during both systole and diastole. The conduit penetrates into the left ventricle in order to prevent tissue growth and occlusions over an opening of the conduit. The ""682 patent and ""397 application also describe an embodiment where a portion of the implant passing through the heart wall is an open structural member lined by polyester (e.g., Dacron). A further embodiment discloses a portion of the implant in a coronary vessel as being an open cell, balloon-expandable stent.
U.S. Pat. No. 5,429,144 to Wilk dated Jul. 4, 1995 teaches implants which are passed through the vasculature in a collapsed state and expanded when placed in the myocardium so as not to extend into either the coronary artery or the left ventricle. The described implants close once per cycle of the heart (e.g., during diastole in the embodiment of FIGS. 7A and 7B or during systole in the embodiment of FIGS. 2A and 2B). Either of these two designs may be lined with a graft.
Commonly assigned and co-pending U.S. patent application Ser. No. 08/944,313 filed Oct. 6, 1997, entitled xe2x80x9cTransmyocardial Implantxe2x80x9d, and filed in the name of inventors Katherine S. Tweden, Guy P. Vanney and Thomas L. Odland, teaches an implant such as that shown in the aforementioned ""397 application and ""682 patent with an enhanced fixation structure. The enhanced fixation structure includes a fabric surrounding at least a portion of the conduit to facilitate tissue growth on the exterior of the implant.
PCT International Application Publication No. WO 98/08456 describes a protrusive stent to form a passageway from the heart to a coronary vessel. The stent is described as wire mesh or other metal or polymeric material and may be self-expanding or pressure expandable. The application describes the stent may be covered by a partial or complete tubular covering of material including polyester, woven polyester, polytetraflouroethylene, expanded polytetraflouroethylene, polyurethane, silicone, polycarbonate, autologous tissue and xenograft tissue.
Biocompatibility is an important design feature. Solid metal implants are formed of material (e.g., titanium or pyrolytic carbon) with low incidents of thrombus and platelet activation. While such materials are proven in use in a wide variety of products (e.g., heart valve components), they do not facilitate fall healing. By xe2x80x9chealingxe2x80x9d, it is meant that over time, the patient""s cells grow over the material of the implant so that blood flowing through the implant is exposed only (or at least primarily) to the patient""s cells rather than to a foreign material.
According to a preferred embodiment of the present invention, a transmyocardial implant is disclosed for establishing a blood flow path through a myocardium between a heart chamber and a lumen of a coronary vessel residing on an exterior of the heart. The implant includes a coronary portion sized to be received with the vessel. A myocardial portion is sized to pass through the myocardium into the heart chamber. A transition portion connects the coronary and myocardial portions for directing blood flow from the myocardial portion and into the coronary portion. The coronary portion and the myocardial portion have an open construction for permitting tissue growth across a wall thickness of the coronary portion and the myocardial portion. The myocardial portion includes an agent for controlling the coagulation cascade and platelet activation, and promoting healing.